SITE INFORMATION AND CORRESPONDENCE

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h w i Jay's Mini Mart Page 2 3302 North West Lane October 1,2008 Stockton, California 95204 The cumulative excess cancer risk calculated using the Johnson and Ettinger model was 2.63 E-06, exceeding the 1.0 E-06 factor for residential receptors, but below the 1.0 E-05 cancer risk factor for commercial receptors. The EHD discussed the results from the Johnson and Ettinger vapor intrusion model with the Central Valley Regional Water Quality Control Board (CVRWQCB) on September 17, 2008. In general, the CVRWQCB prefers soil vapor samples be collected to evaluate the potential for vapor intrusion into buildings. Because the cumulative excess cancer risk factor was exceeded for residential receptors, the CVRWQCB recommended that soil vapor samples be collected to evaluate the potential for vapor intrusion. In view of the questionable soil and groundwater concentrations entered into the Johnson and Ettinger model, the result from the Johnson and Ettinger model that demonstrated the cancer risk factor was exceeded for residential receptor, and the CVRWQCB recommendation, the EHD directs that you submit a work plan by December 1, 2008, for soil vapor sample collection to assess the potential for vapor intrusion into the existing onsite buildings. ATC also provided information concerning sensitive receptors within 2,000 feet of the site and included a number of associated maps. Included was a copy of the USFWS National Wetlands Inventory map that lacked the site location and the "ponds identified as designated wetlands on the large industrial property to the south-southwest." Please resubmit the map showing locations for Jay's Mini-Mart and ponds identified as designated wetlands. ATC also stated that 57 active wells exist within a half-mile of the site; however, the map labeled Environmental Sensitive Receptors illustrated only 56 wells. In Section 7.1.2 of the report, ATC presented Map ID #53 as a domestic well, Map ID#54 as an irrigation well, and Map ID #55 as a municipal well; Section 7.15 stated that the closest domestic well was #53, and #55 was a municipal well. This information may be correct; however, the legend and the map labeled Environmental Sensitive Receptors do not reflect this information. Please resubmit the map showing the appropriate revisions to the EHD by November 7, 2008. Section 7.13 of the report stated that "the mass associated with the dissolved- and adsorbed-phase contaminants is negligible;" as a result, no mass calculation has been submitted. During the meeting on September 17, 2008, the CVRWQCB requested that closure reports include mass removed, mass remaining, and an estimate of when the existing mass will attenuate. Please provide this information to the EHD by November 7, 2008. If you have any questions, please contact Vicki McCartney, Senior Registered Environmental Health Specialist, at(209)468-9852 or by electronic mail at vmccartney@sjcehd.com. Sincerely, Victoria L. McCartney, REHS Nuel C. Henderson, Jr., PG Senior Registered Environmental Hea th Specialist Engineering Geologist c: Ms. Jeanne Homsey, PE, ATC Associates Inc., 1117 Lone Palm Avenue, Suite 201, Modesto, California 95351 Mr. James L.L. Barton, PG, California Regional Water Quality Control Board Central Valley Region, 11020 Sun Center Drive, Suite 200,Rancho Cordova, California 95670